TCP Performance

Nick Olsen nick at flhsi.com
Tue Aug 27 14:49:17 UTC 2013


Duplex mismatch has been checked across the board. On every device.

Nick Olsen
Network Operations (855) FLSPEED  x106

----------------------------------------
From: "Chad Dailey" <nanog at thedaileyplanet.com>
Sent: Tuesday, August 27, 2013 10:48 AM
To: nick at flhsi.com
Subject: Re: TCP Performance

Check for duplex mismatch at the server.  

On Mon, Aug 26, 2013 at 2:07 PM, Nick Olsen <nick at flhsi.com> wrote:
Greetings all, I've got an issue I was hoping to put a few more eyes on.
 Here's the scenario. Downloading a file at our Border is multiple orders
of magnitude faster then a few hops out. Using the same 128MB test file, I
tested at two different locations. As well as between them. Using multiple
connections improves throughput, However it's the single stream issue 
we're
looking at right now. All testing servers in question are Centos Linux.
 Orlando Datapath: Cogent>Orlando Border Router (Mikrotik)>HP Procurve
Switch> Server Results: 2013-08-29 05:04:09 (52.6 MB/s) - `128mbfile.tgz'
saved [127926272/127926272]
 Cocoa NOC Datapath: Cogent>Orlando Border Router (Mikrotik)>Licensed
Microwave Link (300+Mb/s Capacity)>East Orange Router (Mikrotik)> Licensed
Microwave Link (300+Mb/s Capacity)>Cocoa Router (Mikrotik)>Licensed
Microwave Link (300+Mb/s Capacity)>Colo Router (Mikrotik)>NOC Router
(Mikrotik)>HP Procurve Switch>Server Results: 2013-08-26 13:42:25 (398
KB/s) - `128mbfile.tgz' saved [127926272/127926272]
 Orlando-Cocoa NOC Datapath: Orlando Server>HP Procurve Switch>Orlando
Border Router (Mikrotik)>Licensed Microwave Link (300+Mb/s Capacity)>East
Orange Router (Mikrotik)> Licensed Microwave Link (300+Mb/s 
Capacity)>Cocoa
Router (Mikrotik)>Licensed Microwave Link (300+Mb/s Capacity)>Colo Router
(Mikrotik)>NOC Router(Mikrotik)>HP Procurve Switch>ServerResults:
2013-08-26 13:56:25 (3.31 MB/s) - `128mbfile.tgz' saved
[134217728/134217728]
 Now, For the fun of it. I ran Iperf single TCP between our Cocoa and
Orlando POP's. Just like the HTTP test above. (Server has a 100Mb/s port).
It maxes out the port, Unlike the HTTP test.
 [root at ded01 ~]# iperf -c
208.90.219.18------------------------------------------------------------Cli

ent connecting to 208.90.219.18, TCP port 5001TCP window size: 16.0 KByte
(default)------------------------------------------------------------[  3]
local 206.208.56.130 port 47281 connected with 208.90.219.18 port 5001[ 
ID]
Interval       Transfer     Bandwidth[  3]  0.0-10.0 sec   114 MBytes  
95.7
Mbits/sec

Here's associated packet captures for each transfer. As well as full wget
output and traceroutes for each test. As you can see, The tests crossing
the wireless links show about 3x more TCP re-transmits/dup ACK's. But I'm
not sure I'm sold this could show such a huge drop in throughput. Other
then that, nothing really stands out to me as to why these transfers are 
so
much slower. Intra-network iperf testing shows full throughput the whole
way with single connection. As well as UDP testing. One thing to note is
the Iperf testing has far less TCP re-transmit/dup acks then any of the
HTTP testing, Crossing the same Microwave Links and routers.
http://cdn.141networks.com/files/captures.zip
I appreciate any insight anyone might have. Thanks!
 Nick Olsen
Network Operations (855) FLSPEED  x106




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